Common wheat

Nitrogen represents the most important element for the cultivation of wheat as it has a decisive influence on its production, both in terms of yield and quality.
It influences the growth and vegetative vigor of the plants which respond with a very intense green foliage.
In the soil, nitrogen is present in organic form and, in a small amount, in ammoniacal form. Organic nitrogen makes up a large part of the organic substance of the soil and is made up of compounds of animal and vegetable origin (crop residues).
Ammoniacal nitrogen has a positive electric charge (NH₄⁺), therefore it is retained by the soil components with negative electric charge - Cation Exchange Capacity or C.E.C - and is not washed out.
Nitric nitrogen (NO₃^-) derives from the mineralization of the organic substance and through the nitrification of ammonia or urea nitrogen made by nitrogen fertilizers; having a negative electric charge, it is not retained by the soil colloids and is therefore easily leached into the soil.

Phosphorus increases the resistance of wheat to lodging and some biotic adversities. In the soil it is present in organic and inorganic combinations, but only a small part of it is available for the plant since the wheat absorbs only soluble inorganic phosphates.
Phosphorus has irreplaceable functions since it is among the constituents of lecithins and nucleoproteins which play an essential role in the qualitative aspects of the caryopsis.
In the organic form, phosphorus is found in organic matter and humus and is not available for plants, but first it must be transformed through mineralization into soluble phosphates.
Inorganic phosphorus is present in the soil in predominantly insoluble forms, therefore little available for plants.
The most important phosphate fertilizer is superphosphate, simple and triple. Then there are concentrated and bone superphosphate, ammonium phosphates and Thomas slag.
The lack of phosphorus causes a delay and a less growth and a stunted formation of seeds in the plants; moreover, the leaves, starting from those placed higher up, can take on an anthocyanin pigmentation.

Potassium is found in the soil in the form of inorganic salts or adsorbed on the clay-humic complex (C.E.C.). Sandy soils and in any case all those poor in clay and organic matter are poorly endowed with potassium.
Italian soils have a potassium content normally sufficient to meet the needs of wheat; among other things, this cereal does not have high requirements in potassium, therefore it is not generally necessary to add it, except only in the case of particularly deficient soils. Like phosphorus, potassium also helps to limit the lodging of plants.
The most important roles within plants include: regulation of water exchange, active participation in the metabolism of sugars, regulation of protein synthesis and action on cell division.
The most common fertilizers are chloride and potassium sulphate; the latter is preferred for the presence of sulfur and for the low chlorine content which reduces the absorption of nitrogen.

Calcium is a fundamental component of cell walls and also has a direct influence on the regulation of enzymatic systems, on the activity of phytohormones and on the absorption of nutrients.
In wheat, calcium is important in order to have a plant with a normal appearance and healthy foliage.
Calcium deficiency rarely occurs in wheat. Any deficiency symptoms begin to show on the younger parts with an elongated slit in the central section of the leaves. It is easily recognizable with the flag leaf curled or wrinkled.

Magnesium is the central component of "green effect" chlorophyll and improves the effectiveness of the photosynthetic process. It is essential for the synthesis, transport and storage of substances that constitute the plant such as carbohydrates, proteins, fats.
The first symptom of deficiency is chlorosis, which, starting from the leaf apex, mainly affects the older leaves which turn pale green (low concentrations of chlorophyll, easy to identify by looking at the leaf against the light). Chlorosis and necrosis can be observed in severe cases starting from the leaf apices. The growth of the plant is stunted.
Drought can cause similar symptoms of necrosis on the margins.

Wheat cultivation benefits significantly from crop rotation. Maize, chard, tomato, potato, sunflower, soybeans are good cultivation precessions, because wheat is able to use the residue of fertility left in the soil by these crops very well, even better if it is not other cereals. Wheat, however, is not the best crop to use the high fertility left by long-term meadows (legumes and grasses). In arid areas, the succession of wheat to fallow is traditional, where the organic substance of the soil is mineralized and enriched with water. The succession to a renewal crop also allows a less deep tillage, sod seeding or minimum tillage.

Fertilization

The nitrogen content in the soil is often not sufficient to satisfy the cultivation needs, both for the scarce presence and for the delayed response with respect to the needs of the single phenological phases. During the cold months, both mineralization and nitrification processes are practically suspended due to low temperatures (except for rare and temporary occasions of warmth); they will resume in the spring with the heating of the soil, but too late compared to the need for the wheat in the rising phase.
Phosphorus and potassium cannot be washed out as they are adsorbed by the soil and are released into the circulating solution as the crop absorbs them: it is therefore sufficient to integrate the soil, if insufficient, with pre-sowing fertilizations.
During the cold months in which the wheat carries out the long phase of tillage, it can only count on the residual nitric nitrogen of the previous crop, the quantity of which varies according to the organic matter content of the soil, the mineralization rate and the residue of fertilization not used by the previous crop. Furthermore, this small portion of residual nitric nitrogen can be washed away, in whole or in part, by the autumn/winter rains. In conclusion, the soil is a bad supplier of nitrogen for wheat. Considering that this element is the main factor of the quantitative-qualitative yield of wheat and that the supply of nitric nitrogen is scarce and late, it follows that the farmer must intervene with nitrogen fertilizer contributions according to the requirement in each development phase.

Time of fertilization.

Phospho-potassium fertilization.
Phosphorus and potassium are retained by the soil and have very little mobility. Therefore it is necessary that they are buried up to the depth in which the roots will develop.

Nitrogen fertilization.
The best nitrogen fertilization technique is to distribute the nitrogen not long before the period of use by the crop to minimize the risk of leaching. Therefore abundant fertilization when sowing is not recommended, also given the limited initial needs of the crop and the presumed "old strength" present in the soil.
Only after exploiting crops and/or after burying the straw, an additional supply of 20-40 kg per hectare of nitrogen can be useful at sowing, together with the phosphate fertilizer (Biammonic phosphate 18-46-0).
Apart from the case mentioned above, all nitrogen requirements can be met with top dressing fertilizations: the best technique involves 2-3 fertilizations:
- the first, in the month of January to favor tillering; it could be omitted if the crop is in good development conditions and of an intense green color, otherwise it should be done with 15-20% of the total expected dose (Calcium nitrate);
- the second, indispensable in February, to favor the color change and morphogenesis of the ears, distributing 35-40% of the total (ammonium nitrate);
- the third, fundamental in March, just before the start of the rising, to ensure the satisfaction of the very high needs during the rising: this distributing the remaining share of 45-50% of the total (Urea 46%).